android 开发 对图片编码，并生成gif图片

demo场景：

将2张静态的png格式图片组合生成一个gif图片，间隔500毫秒，关键类：AnimatedGifEncoder

如需要解析gif获取每帧的图片，可参考上一篇博客：《android 开发 解码gif图片，获取每帧bitmap》

使用方法：

/**
     * 生成gif图片
     */
    void makeGif()
    {
        String path = Environment.getExternalStorageDirectory().getAbsolutePath() +"/data/data/"+ this.getPackageName()+"/cache";
        Bitmap bmp1 = BitmapFactory.decodeResource(getResources(), R.drawable.gif10); //png格式资源图片
        Bitmap bmp2 = BitmapFactory.decodeResource(getResources(), R.drawable.gif13);//png格式资源图片
        File pathFile = new File(path);
        File gifFile = new File(pathFile,"add_1.gif");
        if(!pathFile.exists())
            pathFile.mkdirs();
        if(!gifFile.exists())
            try {
                gifFile.createNewFile();
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
        OutputStream os;
        try {
            os = new FileOutputStream(gifFile);
            gifEncoder.start(os);  //注意顺序
            gifEncoder.addFrame(bmp1);
            gifEncoder.addFrame(bmp2);
            gifEncoder.setDelay(500);
            gifEncoder.setRepeat(0);
            gifEncoder.finish();  
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

关键的编码gif代码：

import java.io.IOException;
import java.io.OutputStream;

import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Paint;

public class AnimatedGifEncoder {

      protected int width; // image size

      protected int height;
      
      protected int x = 0;
      
      protected int y = 0;

      protected int transparent = -1; // transparent color if given

      protected int transIndex; // transparent index in color table

      protected int repeat = -1; // no repeat

      protected int delay = 0; // frame delay (hundredths)

      protected boolean started = false; // ready to output frames

      protected OutputStream out;

      protected Bitmap image; // current frame

      protected byte[] pixels; // BGR byte array from frame

      protected byte[] indexedPixels; // converted frame indexed to palette

      protected int colorDepth; // number of bit planes

      protected byte[] colorTab; // RGB palette

      protected boolean[] usedEntry = new boolean[256]; // active palette entries

      protected int palSize = 7; // color table size (bits-1)

      protected int dispose = -1; // disposal code (-1 = use default)

      protected boolean closeStream = false; // close stream when finished

      protected boolean firstFrame = true;

      protected boolean sizeSet = false; // if false, get size from first frame

      protected int sample = 10; // default sample interval for quantizer

      /**
       * Sets the delay time between each frame, or changes it for subsequent frames
       * (applies to last frame added).
       * 
       * @param ms
       *          int delay time in milliseconds
       */
      public void setDelay(int ms) {
        delay = ms / 10;
      }

      /**
       * Sets the GIF frame disposal code for the last added frame and any
       * subsequent frames. Default is 0 if no transparent color has been set,
       * otherwise 2.
       * 
       * @param code
       *          int disposal code.
       */
      public void setDispose(int code) {
        if (code >= 0) {
          dispose = code;
        }
      }

      /**
       * Sets the number of times the set of GIF frames should be played. Default is
       * 1; 0 means play indefinitely. Must be invoked before the first image is
       * added.
       * 
       * @param iter
       *          int number of iterations.
       * @return
       */
      public void setRepeat(int iter) {
        if (iter >= 0) {
          repeat = iter;
        }
      }

      /**
       * Sets the transparent color for the last added frame and any subsequent
       * frames. Since all colors are subject to modification in the quantization
       * process, the color in the final palette for each frame closest to the given
       * color becomes the transparent color for that frame. May be set to null to
       * indicate no transparent color.
       * 
       * @param c
       *          Color to be treated as transparent on display.
       */
      public void setTransparent(int c) {
        transparent = c;
      }

      /**
       * Adds next GIF frame. The frame is not written immediately, but is actually
       * deferred until the next frame is received so that timing data can be
       * inserted. Invoking <code>finish()</code> flushes all frames. If
       * <code>setSize</code> was not invoked, the size of the first image is used
       * for all subsequent frames.
       * 
       * @param im
       *          BufferedImage containing frame to write.
       * @return true if successful.
       */
      public boolean addFrame(Bitmap im) {
        if ((im == null) || !started) {
          return false;
        }
        boolean ok = true;
        try {
          if (!sizeSet) {
            // use first frame's size
            setSize(im.getWidth(), im.getHeight());
          }
          image = im;
          getImagePixels(); // convert to correct format if necessary
          analyzePixels(); // build color table & map pixels
          if (firstFrame) {
            writeLSD(); // logical screen descriptior
            writePalette(); // global color table
            if (repeat >= 0) {
              // use NS app extension to indicate reps
              writeNetscapeExt();
            }
          }
          writeGraphicCtrlExt(); // write graphic control extension
          writeImageDesc(); // image descriptor
          if (!firstFrame) {
            writePalette(); // local color table
          }
          writePixels(); // encode and write pixel data
          firstFrame = false;
        } catch (IOException e) {
          ok = false;
        }

        return ok;
      }

      /**
       * Flushes any pending data and closes output file. If writing to an
       * OutputStream, the stream is not closed.
       */
      public boolean finish() {
        if (!started)
          return false;
        boolean ok = true;
        started = false;
        try {
          out.write(0x3b); // gif trailer
          out.flush();
          if (closeStream) {
            out.close();
          }
        } catch (IOException e) {
          ok = false;
        }

        // reset for subsequent use
        transIndex = 0;
        out = null;
        image = null;
        pixels = null;
        indexedPixels = null;
        colorTab = null;
        closeStream = false;
        firstFrame = true;

        return ok;
      }

      /**
       * Sets frame rate in frames per second. Equivalent to
       * <code>setDelay(1000/fps)</code>.
       * 
       * @param fps
       *          float frame rate (frames per second)
       */
      public void setFrameRate(float fps) {
        if (fps != 0f) {
          delay = (int)(100 / fps);
        }
      }

      /**
       * Sets quality of color quantization (conversion of images to the maximum 256
       * colors allowed by the GIF specification). Lower values (minimum = 1)
       * produce better colors, but slow processing significantly. 10 is the
       * default, and produces good color mapping at reasonable speeds. Values
       * greater than 20 do not yield significant improvements in speed.
       * 
       * @param quality
       *          int greater than 0.
       * @return
       */
      public void setQuality(int quality) {
        if (quality < 1)
          quality = 1;
        sample = quality;
      }

      /**
       * Sets the GIF frame size. The default size is the size of the first frame
       * added if this method is not invoked.
       * 
       * @param w
       *          int frame width.
       * @param h
       *          int frame width.
       */
      public void setSize(int w, int h) {
        width = w;
        height = h;
        if (width < 1)
          width = 320;
        if (height < 1)
          height = 240;
        sizeSet = true;
      }
      
      /**
       * Sets the GIF frame position. The position is 0,0 by default.
       * Useful for only updating a section of the image
       * 
       * @param w
       *          int frame width.
       * @param h
       *          int frame width.
       */
      public void setPosition(int x, int y) {
         this.x = x;
         this.y = y;
      }

      /**
       * Initiates GIF file creation on the given stream. The stream is not closed
       * automatically.
       * 
       * @param os
       *          OutputStream on which GIF images are written.
       * @return false if initial write failed.
       */
      public boolean start(OutputStream os) {
        if (os == null)
          return false;
        boolean ok = true;
        closeStream = false;
        out = os;
        try {
          writeString("GIF89a"); // header
        } catch (IOException e) {
          ok = false;
        }
        return started = ok;
      }

      /**
       * Analyzes image colors and creates color map.
       */
      protected void analyzePixels() {
        int len = pixels.length;
        int nPix = len / 3;
        indexedPixels = new byte[nPix];
        NeuQuant nq = new NeuQuant(pixels, len, sample);
        // initialize quantizer
        colorTab = nq.process(); // create reduced palette
        // convert map from BGR to RGB
        for (int i = 0; i < colorTab.length; i += 3) {
          byte temp = colorTab[i];
          colorTab[i] = colorTab[i + 2];
          colorTab[i + 2] = temp;
          usedEntry[i / 3] = false;
        }
        // map image pixels to new palette
        int k = 0;
        for (int i = 0; i < nPix; i++) {
          int index = nq.map(pixels[k++] & 0xff, pixels[k++] & 0xff, pixels[k++] & 0xff);
          usedEntry[index] = true;
          indexedPixels[i] = (byte) index;
        }
        pixels = null;
        colorDepth = 8;
        palSize = 7;
        // get closest match to transparent color if specified
        if (transparent != -1) {
          transIndex = findClosest(transparent);
        }
      }

      /**
       * Returns index of palette color closest to c
       * 
       */
      protected int findClosest(int c) {
        if (colorTab == null)
          return -1;
        int r = (c >> 16) & 0xff;
        int g = (c >> 8) & 0xff;
        int b = (c >> 0) & 0xff;
        int minpos = 0;
        int dmin = 256 * 256 * 256;
        int len = colorTab.length;
        for (int i = 0; i < len;) {
          int dr = r - (colorTab[i++] & 0xff);
          int dg = g - (colorTab[i++] & 0xff);
          int db = b - (colorTab[i] & 0xff);
          int d = dr * dr + dg * dg + db * db;
          int index = i / 3;
          if (usedEntry[index] && (d < dmin)) {
            dmin = d;
            minpos = index;
          }
          i++;
        }
        return minpos;
      }

      /**
       * Extracts image pixels into byte array "pixels"
       */
      protected void getImagePixels() {
        int w = image.getWidth();
        int h = image.getHeight();
        if ((w != width) || (h != height)) {
          // create new image with right size/format
          Bitmap temp = Bitmap.createBitmap(width, height, Config.RGB_565);
          Canvas g = new Canvas(temp);
          g.drawBitmap(image, 0, 0, new Paint());
          image = temp;
        }
        int[] data = getImageData(image);
        pixels = new byte[data.length * 3];
        for (int i = 0; i < data.length; i++) {
            int td = data[i];
            int tind = i * 3;
            pixels[tind++] = (byte) ((td >> 0) & 0xFF);
            pixels[tind++] = (byte) ((td >> 8) & 0xFF);
            pixels[tind] = (byte) ((td >> 16) & 0xFF);
        }
      }
      protected int[] getImageData(Bitmap img) {
            int w = img.getWidth();
            int h = img.getHeight();

            int[] data = new int[w * h];
            img.getPixels(data, 0, w, 0, 0, w, h);
            return data;
        }

      /**
       * Writes Graphic Control Extension
       */
      protected void writeGraphicCtrlExt() throws IOException {
        out.write(0x21); // extension introducer
        out.write(0xf9); // GCE label
        out.write(4); // data block size
        int transp, disp;
        if (transparent == -1) {
          transp = 0;
          disp = 0; // dispose = no action
        } else {
          transp = 1;
          disp = 2; // force clear if using transparent color
        }
        if (dispose >= 0) {
          disp = dispose & 7; // user override
        }
        disp <<= 2;

        // packed fields
        out.write(0 | // 1:3 reserved
            disp | // 4:6 disposal
            0 | // 7 user input - 0 = none
            transp); // 8 transparency flag

        writeShort(delay); // delay x 1/100 sec
        out.write(transIndex); // transparent color index
        out.write(0); // block terminator
      }

      /**
       * Writes Image Descriptor
       */
      protected void writeImageDesc() throws IOException {
        out.write(0x2c); // image separator
        writeShort(x); // image position x,y = 0,0
        writeShort(y);
        writeShort(width); // image size
        writeShort(height);
        // packed fields
        if (firstFrame) {
          // no LCT - GCT is used for first (or only) frame
          out.write(0);
        } else {
          // specify normal LCT
          out.write(0x80 | // 1 local color table 1=yes
              0 | // 2 interlace - 0=no
              0 | // 3 sorted - 0=no
              0 | // 4-5 reserved
              palSize); // 6-8 size of color table
        }
      }

      /**
       * Writes Logical Screen Descriptor
       */
      protected void writeLSD() throws IOException {
        // logical screen size
        writeShort(width);
        writeShort(height);
        // packed fields
        out.write((0x80 | // 1 : global color table flag = 1 (gct used)
            0x70 | // 2-4 : color resolution = 7
            0x00 | // 5 : gct sort flag = 0
            palSize)); // 6-8 : gct size

        out.write(0); // background color index
        out.write(0); // pixel aspect ratio - assume 1:1
      }

      /**
       * Writes Netscape application extension to define repeat count.
       */
      protected void writeNetscapeExt() throws IOException {
        out.write(0x21); // extension introducer
        out.write(0xff); // app extension label
        out.write(11); // block size
        writeString("NETSCAPE" + "2.0"); // app id + auth code
        out.write(3); // sub-block size
        out.write(1); // loop sub-block id
        writeShort(repeat); // loop count (extra iterations, 0=repeat forever)
        out.write(0); // block terminator
      }

      /**
       * Writes color table
       */
      protected void writePalette() throws IOException {
        out.write(colorTab, 0, colorTab.length);
        int n = (3 * 256) - colorTab.length;
        for (int i = 0; i < n; i++) {
          out.write(0);
        }
      }

      /**
       * Encodes and writes pixel data
       */
      protected void writePixels() throws IOException {
        LZWEncoder encoder = new LZWEncoder(width, height, indexedPixels, colorDepth);
        encoder.encode(out);
      }

      /**
       * Write 16-bit value to output stream, LSB first
       */
      protected void writeShort(int value) throws IOException {
        out.write(value & 0xff);
        out.write((value >> 8) & 0xff);
      }

      /**
       * Writes string to output stream
       */
      protected void writeString(String s) throws IOException {
        for (int i = 0; i < s.length(); i++) {
          out.write((byte) s.charAt(i));
        }
      }
    }

    /*
     * NeuQuant Neural-Net Quantization Algorithm
     * ------------------------------------------
     * 
     * Copyright (c) 1994 Anthony Dekker
     * 
     * NEUQUANT Neural-Net quantization algorithm by Anthony Dekker, 1994. See
     * "Kohonen neural networks for optimal colour quantization" in "Network:
     * Computation in Neural Systems" Vol. 5 (1994) pp 351-367. for a discussion of
     * the algorithm.
     * 
     * Any party obtaining a copy of these files from the author, directly or
     * indirectly, is granted, free of charge, a full and unrestricted irrevocable,
     * world-wide, paid up, royalty-free, nonexclusive right and license to deal in
     * this software and documentation files (the "Software"), including without
     * limitation the rights to use, copy, modify, merge, publish, distribute,
     * sublicense, and/or sell copies of the Software, and to permit persons who
     * receive copies from any such party to do so, with the only requirement being
     * that this copyright notice remain intact.
     */

//     Ported to Java 12/00 K Weiner
    class NeuQuant {

      protected static final int netsize = 256; /* number of colours used */

      /* four primes near 500 - assume no image has a length so large */
      /* that it is divisible by all four primes */
      protected static final int prime1 = 499;

      protected static final int prime2 = 491;

      protected static final int prime3 = 487;

      protected static final int prime4 = 503;

      protected static final int minpicturebytes = (3 * prime4);

      /* minimum size for input image */

      /*
       * Program Skeleton ---------------- [select samplefac in range 1..30] [read
       * image from input file] pic = (unsigned char*) malloc(3*width*height);
       * initnet(pic,3*width*height,samplefac); learn(); unbiasnet(); [write output
       * image header, using writecolourmap(f)] inxbuild(); write output image using
       * inxsearch(b,g,r)
       */

      /*
       * Network Definitions -------------------
       */

      protected static final int maxnetpos = (netsize - 1);

      protected static final int netbiasshift = 4; /* bias for colour values */

      protected static final int ncycles = 100; /* no. of learning cycles */

      /* defs for freq and bias */
      protected static final int intbiasshift = 16; /* bias for fractions */

      protected static final int intbias = (((int) 1) << intbiasshift);

      protected static final int gammashift = 10; /* gamma = 1024 */

      protected static final int gamma = (((int) 1) << gammashift);

      protected static final int betashift = 10;

      protected static final int beta = (intbias >> betashift); /* beta = 1/1024 */

      protected static final int betagamma = (intbias << (gammashift - betashift));

      /* defs for decreasing radius factor */
      protected static final int initrad = (netsize >> 3); /*
                                                             * for 256 cols, radius
                                                             * starts
                                                             */

      protected static final int radiusbiasshift = 6; /* at 32.0 biased by 6 bits */

      protected static final int radiusbias = (((int) 1) << radiusbiasshift);

      protected static final int initradius = (initrad * radiusbias); /*
                                                                       * and
                                                                       * decreases
                                                                       * by a
                                                                       */

      protected static final int radiusdec = 30; /* factor of 1/30 each cycle */

      /* defs for decreasing alpha factor */
      protected static final int alphabiasshift = 10; /* alpha starts at 1.0 */

      protected static final int initalpha = (((int) 1) << alphabiasshift);

      protected int alphadec; /* biased by 10 bits */

      /* radbias and alpharadbias used for radpower calculation */
      protected static final int radbiasshift = 8;

      protected static final int radbias = (((int) 1) << radbiasshift);

      protected static final int alpharadbshift = (alphabiasshift + radbiasshift);

      protected static final int alpharadbias = (((int) 1) << alpharadbshift);

      /*
       * Types and Global Variables --------------------------
       */

      protected byte[] thepicture; /* the input image itself */

      protected int lengthcount; /* lengthcount = H*W*3 */

      protected int samplefac; /* sampling factor 1..30 */

      // typedef int pixel[4]; /* BGRc */
      protected int[][] network; /* the network itself - [netsize][4] */

      protected int[] netindex = new int[256];

      /* for network lookup - really 256 */

      protected int[] bias = new int[netsize];

      /* bias and freq arrays for learning */
      protected int[] freq = new int[netsize];

      protected int[] radpower = new int[initrad];

      /* radpower for precomputation */

      /*
       * Initialise network in range (0,0,0) to (255,255,255) and set parameters
       * -----------------------------------------------------------------------
       */
      public NeuQuant(byte[] thepic, int len, int sample) {

        int i;
        int[] p;

        thepicture = thepic;
        lengthcount = len;
        samplefac = sample;

        network = new int[netsize][];
        for (i = 0; i < netsize; i++) {
          network[i] = new int[4];
          p = network[i];
          p[0] = p[1] = p[2] = (i << (netbiasshift + 8)) / netsize;
          freq[i] = intbias / netsize; /* 1/netsize */
          bias[i] = 0;
        }
      }

      public byte[] colorMap() {
        byte[] map = new byte[3 * netsize];
        int[] index = new int[netsize];
        for (int i = 0; i < netsize; i++)
          index[network[i][3]] = i;
        int k = 0;
        for (int i = 0; i < netsize; i++) {
          int j = index[i];
          map[k++] = (byte) (network[j][0]);
          map[k++] = (byte) (network[j][1]);
          map[k++] = (byte) (network[j][2]);
        }
        return map;
      }

      /*
       * Insertion sort of network and building of netindex[0..255] (to do after
       * unbias)
       * -------------------------------------------------------------------------------
       */
      public void inxbuild() {

        int i, j, smallpos, smallval;
        int[] p;
        int[] q;
        int previouscol, startpos;

        previouscol = 0;
        startpos = 0;
        for (i = 0; i < netsize; i++) {
          p = network[i];
          smallpos = i;
          smallval = p[1]; /* index on g */
          /* find smallest in i..netsize-1 */
          for (j = i + 1; j < netsize; j++) {
            q = network[j];
            if (q[1] < smallval) { /* index on g */
              smallpos = j;
              smallval = q[1]; /* index on g */
            }
          }
          q = network[smallpos];
          /* swap p (i) and q (smallpos) entries */
          if (i != smallpos) {
            j = q[0];
            q[0] = p[0];
            p[0] = j;
            j = q[1];
            q[1] = p[1];
            p[1] = j;
            j = q[2];
            q[2] = p[2];
            p[2] = j;
            j = q[3];
            q[3] = p[3];
            p[3] = j;
          }
          /* smallval entry is now in position i */
          if (smallval != previouscol) {
            netindex[previouscol] = (startpos + i) >> 1;
            for (j = previouscol + 1; j < smallval; j++)
              netindex[j] = i;
            previouscol = smallval;
            startpos = i;
          }
        }
        netindex[previouscol] = (startpos + maxnetpos) >> 1;
        for (j = previouscol + 1; j < 256; j++)
          netindex[j] = maxnetpos; /* really 256 */
      }

      /*
       * Main Learning Loop ------------------
       */
      public void learn() {

        int i, j, b, g, r;
        int radius, rad, alpha, step, delta, samplepixels;
        byte[] p;
        int pix, lim;

        if (lengthcount < minpicturebytes)
          samplefac = 1;
        alphadec = 30 + ((samplefac - 1) / 3);
        p = thepicture;
        pix = 0;
        lim = lengthcount;
        samplepixels = lengthcount / (3 * samplefac);
        delta = samplepixels / ncycles;
        alpha = initalpha;
        radius = initradius;

        rad = radius >> radiusbiasshift;
        if (rad <= 1)
          rad = 0;
        for (i = 0; i < rad; i++)
          radpower[i] = alpha * (((rad * rad - i * i) * radbias) / (rad * rad));

        // fprintf(stderr,"beginning 1D learning: initial radius=%d
", rad);

        if (lengthcount < minpicturebytes)
          step = 3;
        else if ((lengthcount % prime1) != 0)
          step = 3 * prime1;
        else {
          if ((lengthcount % prime2) != 0)
            step = 3 * prime2;
          else {
            if ((lengthcount % prime3) != 0)
              step = 3 * prime3;
            else
              step = 3 * prime4;
          }
        }

        i = 0;
        while (i < samplepixels) {
          b = (p[pix + 0] & 0xff) << netbiasshift;
          g = (p[pix + 1] & 0xff) << netbiasshift;
          r = (p[pix + 2] & 0xff) << netbiasshift;
          j = contest(b, g, r);

          altersingle(alpha, j, b, g, r);
          if (rad != 0)
            alterneigh(rad, j, b, g, r); /* alter neighbours */

          pix += step;
          if (pix >= lim)
            pix -= lengthcount;

          i++;
          if (delta == 0)
            delta = 1;
          if (i % delta == 0) {
            alpha -= alpha / alphadec;
            radius -= radius / radiusdec;
            rad = radius >> radiusbiasshift;
            if (rad <= 1)
              rad = 0;
            for (j = 0; j < rad; j++)
              radpower[j] = alpha * (((rad * rad - j * j) * radbias) / (rad * rad));
          }
        }
        // fprintf(stderr,"finished 1D learning: final alpha=%f
        // !
",((float)alpha)/initalpha);
      }

      /*
       * Search for BGR values 0..255 (after net is unbiased) and return colour
       * index
       * ----------------------------------------------------------------------------
       */
      public int map(int b, int g, int r) {

        int i, j, dist, a, bestd;
        int[] p;
        int best;

        bestd = 1000; /* biggest possible dist is 256*3 */
        best = -1;
        i = netindex[g]; /* index on g */
        j = i - 1; /* start at netindex[g] and work outwards */

        while ((i < netsize) || (j >= 0)) {
          if (i < netsize) {
            p = network[i];
            dist = p[1] - g; /* inx key */
            if (dist >= bestd)
              i = netsize; /* stop iter */
            else {
              i++;
              if (dist < 0)
                dist = -dist;
              a = p[0] - b;
              if (a < 0)
                a = -a;
              dist += a;
              if (dist < bestd) {
                a = p[2] - r;
                if (a < 0)
                  a = -a;
                dist += a;
                if (dist < bestd) {
                  bestd = dist;
                  best = p[3];
                }
              }
            }
          }
          if (j >= 0) {
            p = network[j];
            dist = g - p[1]; /* inx key - reverse dif */
            if (dist >= bestd)
              j = -1; /* stop iter */
            else {
              j--;
              if (dist < 0)
                dist = -dist;
              a = p[0] - b;
              if (a < 0)
                a = -a;
              dist += a;
              if (dist < bestd) {
                a = p[2] - r;
                if (a < 0)
                  a = -a;
                dist += a;
                if (dist < bestd) {
                  bestd = dist;
                  best = p[3];
                }
              }
            }
          }
        }
        return (best);
      }

      public byte[] process() {
        learn();
        unbiasnet();
        inxbuild();
        return colorMap();
      }

      /*
       * Unbias network to give byte values 0..255 and record position i to prepare
       * for sort
       * -----------------------------------------------------------------------------------
       */
      public void unbiasnet() {

        int i;

        for (i = 0; i < netsize; i++) {
          network[i][0] >>= netbiasshift;
          network[i][1] >>= netbiasshift;
          network[i][2] >>= netbiasshift;
          network[i][3] = i; /* record colour no */
        }
      }

      /*
       * Move adjacent neurons by precomputed alpha*(1-((i-j)^2/[r]^2)) in
       * radpower[|i-j|]
       * ---------------------------------------------------------------------------------
       */
      protected void alterneigh(int rad, int i, int b, int g, int r) {

        int j, k, lo, hi, a, m;
        int[] p;

        lo = i - rad;
        if (lo < -1)
          lo = -1;
        hi = i + rad;
        if (hi > netsize)
          hi = netsize;

        j = i + 1;
        k = i - 1;
        m = 1;
        while ((j < hi) || (k > lo)) {
          a = radpower[m++];
          if (j < hi) {
            p = network[j++];
            try {
              p[0] -= (a * (p[0] - b)) / alpharadbias;
              p[1] -= (a * (p[1] - g)) / alpharadbias;
              p[2] -= (a * (p[2] - r)) / alpharadbias;
            } catch (Exception e) {
            } // prevents 1.3 miscompilation
          }
          if (k > lo) {
            p = network[k--];
            try {
              p[0] -= (a * (p[0] - b)) / alpharadbias;
              p[1] -= (a * (p[1] - g)) / alpharadbias;
              p[2] -= (a * (p[2] - r)) / alpharadbias;
            } catch (Exception e) {
            }
          }
        }
      }

      /*
       * Move neuron i towards biased (b,g,r) by factor alpha
       * ----------------------------------------------------
       */
      protected void altersingle(int alpha, int i, int b, int g, int r) {

        /* alter hit neuron */
        int[] n = network[i];
        n[0] -= (alpha * (n[0] - b)) / initalpha;
        n[1] -= (alpha * (n[1] - g)) / initalpha;
        n[2] -= (alpha * (n[2] - r)) / initalpha;
      }

      /*
       * Search for biased BGR values ----------------------------
       */
      protected int contest(int b, int g, int r) {

        /* finds closest neuron (min dist) and updates freq */
        /* finds best neuron (min dist-bias) and returns position */
        /* for frequently chosen neurons, freq[i] is high and bias[i] is negative */
        /* bias[i] = gamma*((1/netsize)-freq[i]) */

        int i, dist, a, biasdist, betafreq;
        int bestpos, bestbiaspos, bestd, bestbiasd;
        int[] n;

        bestd = ~(((int) 1) << 31);
        bestbiasd = bestd;
        bestpos = -1;
        bestbiaspos = bestpos;

        for (i = 0; i < netsize; i++) {
          n = network[i];
          dist = n[0] - b;
          if (dist < 0)
            dist = -dist;
          a = n[1] - g;
          if (a < 0)
            a = -a;
          dist += a;
          a = n[2] - r;
          if (a < 0)
            a = -a;
          dist += a;
          if (dist < bestd) {
            bestd = dist;
            bestpos = i;
          }
          biasdist = dist - ((bias[i]) >> (intbiasshift - netbiasshift));
          if (biasdist < bestbiasd) {
            bestbiasd = biasdist;
            bestbiaspos = i;
          }
          betafreq = (freq[i] >> betashift);
          freq[i] -= betafreq;
          bias[i] += (betafreq << gammashift);
        }
        freq[bestpos] += beta;
        bias[bestpos] -= betagamma;
        return (bestbiaspos);
      }
    }

//     ==============================================================================
//     Adapted from Jef Poskanzer's Java port by way of J. M. G. Elliott.
//     K Weiner 12/00

    class LZWEncoder {

      private static final int EOF = -1;

      private int imgW, imgH;

      private byte[] pixAry;

      private int initCodeSize;

      private int remaining;

      private int curPixel;

      // GIFCOMPR.C - GIF Image compression routines
      //
      // Lempel-Ziv compression based on 'compress'. GIF modifications by
      // David Rowley (mgardi@watdcsu.waterloo.edu)

      // General DEFINEs

      static final int BITS = 12;

      static final int HSIZE = 5003; // 80% occupancy

      // GIF Image compression - modified 'compress'
      //
      // Based on: compress.c - File compression ala IEEE Computer, June 1984.
      //
      // By Authors: Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
      // Jim McKie (decvax!mcvax!jim)
      // Steve Davies (decvax!vax135!petsd!peora!srd)
      // Ken Turkowski (decvax!decwrl!turtlevax!ken)
      // James A. Woods (decvax!ihnp4!ames!jaw)
      // Joe Orost (decvax!vax135!petsd!joe)

      int n_bits; // number of bits/code

      int maxbits = BITS; // user settable max # bits/code

      int maxcode; // maximum code, given n_bits

      int maxmaxcode = 1 << BITS; // should NEVER generate this code

      int[] htab = new int[HSIZE];

      int[] codetab = new int[HSIZE];

      int hsize = HSIZE; // for dynamic table sizing

      int free_ent = 0; // first unused entry

      // block compression parameters -- after all codes are used up,
      // and compression rate changes, start over.
      boolean clear_flg = false;

      // Algorithm: use open addressing double hashing (no chaining) on the
      // prefix code / next character combination. We do a variant of Knuth's
      // algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
      // secondary probe. Here, the modular division first probe is gives way
      // to a faster exclusive-or manipulation. Also do block compression with
      // an adaptive reset, whereby the code table is cleared when the compression
      // ratio decreases, but after the table fills. The variable-length output
      // codes are re-sized at this point, and a special CLEAR code is generated
      // for the decompressor. Late addition: construct the table according to
      // file size for noticeable speed improvement on small files. Please direct
      // questions about this implementation to ames!jaw.

      int g_init_bits;

      int ClearCode;

      int EOFCode;

      // output
      //
      // Output the given code.
      // Inputs:
      // code: A n_bits-bit integer. If == -1, then EOF. This assumes
      // that n_bits =< wordsize - 1.
      // Outputs:
      // Outputs code to the file.
      // Assumptions:
      // Chars are 8 bits long.
      // Algorithm:
      // Maintain a BITS character long buffer (so that 8 codes will
      // fit in it exactly). Use the VAX insv instruction to insert each
      // code in turn. When the buffer fills up empty it and start over.

      int cur_accum = 0;

      int cur_bits = 0;

      int masks[] = { 0x0000, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF, 0x01FF,
          0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF };

      // Number of characters so far in this 'packet'
      int a_count;

      // Define the storage for the packet accumulator
      byte[] accum = new byte[256];

      // ----------------------------------------------------------------------------
      LZWEncoder(int width, int height, byte[] pixels, int color_depth) {
        imgW = width;
        imgH = height;
        pixAry = pixels;
        initCodeSize = Math.max(2, color_depth);
      }

      // Add a character to the end of the current packet, and if it is 254
      // characters, flush the packet to disk.
      void char_out(byte c, OutputStream outs) throws IOException {
        accum[a_count++] = c;
        if (a_count >= 254)
          flush_char(outs);
      }

      // Clear out the hash table

      // table clear for block compress
      void cl_block(OutputStream outs) throws IOException {
        cl_hash(hsize);
        free_ent = ClearCode + 2;
        clear_flg = true;

        output(ClearCode, outs);
      }

      // reset code table
      void cl_hash(int hsize) {
        for (int i = 0; i < hsize; ++i)
          htab[i] = -1;
      }

      void compress(int init_bits, OutputStream outs) throws IOException {
        int fcode;
        int i /* = 0 */;
        int c;
        int ent;
        int disp;
        int hsize_reg;
        int hshift;

        // Set up the globals: g_init_bits - initial number of bits
        g_init_bits = init_bits;

        // Set up the necessary values
        clear_flg = false;
        n_bits = g_init_bits;
        maxcode = MAXCODE(n_bits);

        ClearCode = 1 << (init_bits - 1);
        EOFCode = ClearCode + 1;
        free_ent = ClearCode + 2;

        a_count = 0; // clear packet

        ent = nextPixel();

        hshift = 0;
        for (fcode = hsize; fcode < 65536; fcode *= 2)
          ++hshift;
        hshift = 8 - hshift; // set hash code range bound

        hsize_reg = hsize;
        cl_hash(hsize_reg); // clear hash table

        output(ClearCode, outs);

        outer_loop: while ((c = nextPixel()) != EOF) {
          fcode = (c << maxbits) + ent;
          i = (c << hshift) ^ ent; // xor hashing

          if (htab[i] == fcode) {
            ent = codetab[i];
            continue;
          } else if (htab[i] >= 0) // non-empty slot
          {
            disp = hsize_reg - i; // secondary hash (after G. Knott)
            if (i == 0)
              disp = 1;
            do {
              if ((i -= disp) < 0)
                i += hsize_reg;

              if (htab[i] == fcode) {
                ent = codetab[i];
                continue outer_loop;
              }
            } while (htab[i] >= 0);
          }
          output(ent, outs);
          ent = c;
          if (free_ent < maxmaxcode) {
            codetab[i] = free_ent++; // code -> hashtable
            htab[i] = fcode;
          } else
            cl_block(outs);
        }
        // Put out the final code.
        output(ent, outs);
        output(EOFCode, outs);
      }

      // ----------------------------------------------------------------------------
      void encode(OutputStream os) throws IOException {
        os.write(initCodeSize); // write "initial code size" byte

        remaining = imgW * imgH; // reset navigation variables
        curPixel = 0;

        compress(initCodeSize + 1, os); // compress and write the pixel data

        os.write(0); // write block terminator
      }

      // Flush the packet to disk, and reset the accumulator
      void flush_char(OutputStream outs) throws IOException {
        if (a_count > 0) {
          outs.write(a_count);
          outs.write(accum, 0, a_count);
          a_count = 0;
        }
      }

      final int MAXCODE(int n_bits) {
        return (1 << n_bits) - 1;
      }

      // ----------------------------------------------------------------------------
      // Return the next pixel from the image
      // ----------------------------------------------------------------------------
      private int nextPixel() {
        if (remaining == 0)
          return EOF;

        --remaining;

        byte pix = pixAry[curPixel++];

        return pix & 0xff;
      }

      void output(int code, OutputStream outs) throws IOException {
        cur_accum &= masks[cur_bits];

        if (cur_bits > 0)
          cur_accum |= (code << cur_bits);
        else
          cur_accum = code;

        cur_bits += n_bits;

        while (cur_bits >= 8) {
          char_out((byte) (cur_accum & 0xff), outs);
          cur_accum >>= 8;
          cur_bits -= 8;
        }

        // If the next entry is going to be too big for the code size,
        // then increase it, if possible.
        if (free_ent > maxcode || clear_flg) {
          if (clear_flg) {
            maxcode = MAXCODE(n_bits = g_init_bits);
            clear_flg = false;
          } else {
            ++n_bits;
            if (n_bits == maxbits)
              maxcode = maxmaxcode;
            else
              maxcode = MAXCODE(n_bits);
          }
        }

        if (code == EOFCode) {
          // At EOF, write the rest of the buffer.
          while (cur_bits > 0) {
            char_out((byte) (cur_accum & 0xff), outs);
            cur_accum >>= 8;
            cur_bits -= 8;
          }

          flush_char(outs);
        }
      }
    }